Isaac L. Moss

A Novel Thiol-Modified Hyaluronan and Elastin-Like Polypetide Composite Material for Tissue Engineering of the Nucleus Pulposus of the Intervertebral Disc

Study Design. Biomechanical, in vitro, and initial in vivo evaluation of a thiol-modified hyaluronan (TM-HA) and elastin-like polypeptide (ELP) composite hydrogel for nucleus pulposus (NP) tissue engineering. Objective. To investigate the utility of a TM-HA and ELP composite material as a potential tissue-engineering scaffold to reconstitute the NP in early degenerative disc disease (DDD) on the basis of both biomechanical and biologic parameters. Summary of Background Data. DDD is a common ailment with enormous medical, psychosocial, and economic ramifications. Only end-stage surgical therapies are currently widely available. A less invasive, early stage therapy may provide a clinically relevant treatment option. Methods. TM-HA and ELP were combined in various concentrations and cross-linked using poly (ethylene glycol) diacrylate. Resulting materials were evaluated biomechanically using confined com-pression to determine biphasic material properties. In vitro cell culture with human intervertebral disc (IVD) cells seeded within TM-HA/ELP scaffolds was analyzed for cell viability and phenotype. The hydrogels’ materials were evaluated in an established New Zealand White (NZW) rabbit model of DDD. Results. The addition of ELP to TM-HA–based hydrogels resulted in a stiffer construct, which is less stiff than native NP but has time-dependant loading characteristics that may be desirable when injected into the IVD. In vitro experiments demonstrated 70% cell viability at 3 weeks with apparent maintenance of phenotype on the basis of morphologic and immunohistochemical data. The addition of ELP had a positive desirable biomechanical effect but did not have a significant positive or negative biologic effect on cell activity. The in vivo feasibility study demonstrated favorable material characteristics and biocompatibility for application as a minimally invasive injectable NP supplement. Conclusions. TM-HA–based hydrogels provide a hospitable environment for human IVD cells and have material characteristics, particularly when supplemented with ELPs that are attractive for potential application as an injectable NP supplement.

Assessment of biocompatibility and initial evaluation of genipin cross-linked elastin-like polypeptides in the treatment of an osteochondral knee defect in rabbits

Polypeptides based on the alternating hydrophobic and cross-linking domain structure of human elastin are capable of undergoing self-assembly to produce polymeric matrices with unique biological and mechanical properties. Here, we test the initial feasibility of using a genipin cross-linked elastin-based material as an acellular plug in the treatment of an osteochondral defect in the rabbit knee. Full-thickness defects in the weight-bearing surface of the medial femoral condyle in 18 New Zealand White rabbits were surgically produced and press fitted with cylindrical pads composed of genipin cross-linked elastin-like polypeptides, with identical wounds in the opposite knee left untreated as controls. The biocompatibility of the material, overall wound healing and regeneration of subchondral tissue was assessed at 2, 4 and 6weeks by histological evaluation, synovial fluid analysis and microcomputerized tomography scanning. Histological analysis revealed the regeneration of subchondral bone at the periphery of the material, with evidence of hyaline-like overgrowth across the apical surface in 11/16 cases. Pads developed tight contacts with host tissue and appeared completely biocompatible, with no evidence of localized immune response or increased inflammation compared to controls. The material was stable to 6weeks, with an aggregate elastic modulus calculated at approximately 470kPa when tested under confined compression. Further studies are required to assess material degradation over time and long-term replacement with repair tissue.

The Relationship between Preoperative Expectations and the Short-Term Postoperative Satisfaction and Functional Outcome in Lumbar Spine Surgery: A Systematic Review

Study Design Systematic review. Objective To examine the relationship between the patients preoperative expectations and short-term postoperative satisfaction and functional outcome in lumbar spine surgery. Methods The Medline, Embase, and Cochrane databases were queried using a predefined search algorithm to identify all lumbar spine studies analyzing the influence of preoperative expectations on postoperative satisfaction and functional outcome. Two independent reviewers and a third independent mediator reviewed the literature and performed study screening, selection, methodological assessment, and data extraction using an objective protocol. Results Of 444 studies identified, 13 met the inclusion criteria. Methodological quality scores ranged from 59 to 100% with the greatest variability in defining patient characteristics and the methods of assessing patient expectations. Patient expectations were assessed in 22 areas, most frequently back and leg pain expectations and general expectations. Functional outcome was assessed by 13 tools; the most common were the visual analog scale, Oswestry Disability Index (ODI), and Short Form Health Survey (SF-36). Positive expectations for symptomatology, activity, general health, and recovery correlated with satisfaction. General expectations correlated with higher SF-36 Physical Subcomponent scores, better global function, and lower ODI outcome. Conclusions on the influence of the expectations for pain were limited due to the study heterogeneity, but the evidence suggests a positive correlation between the expectation and outcome for back and leg pain. Conclusions Positive expectations correlated significantly with short-term postoperative satisfaction and functional outcome, including higher SF-36 scores, earlier return to work, and decreased ODI scores. Future expectation-based investigations will benefit from implementation of the standardized methods of expectation, satisfaction, and outcome analysis discussed herein.

Allogeneic Articular Chondrocyte Transplantation Downregulates Interleukin 8 Gene Expression in the Degenerating Rabbit Intervertebral Disk In Vivo.

ObjectiveThe aim of this study was to investigate whether repopulating the degenerating intervertebral disk (IVD) with articular chondrocytes will decrease inflammation in the degenerating rabbit IVD. DesignThis was a biologic study in a rabbit IVD-injury model in vivo. Dual cell tracking methods (infrared dye labeling and adenovirus transduction) were used to demonstrate the viability of allogeneic articular chondrocytes injected into degenerating rabbit IVDs. Interleukin 8 gene expression was determined via real-time polymerase chain reaction. Infiltrating inflammatory cells (macrophages, T cells, or neutrophils) were examined with immunohistochemistry. The IVDs were also examined by routine histology. ResultsArticular chondrocytes labeled with infrared dye were detected in the degenerating IVDs at both 2 and 8 wks after injection. At the 2-wk time point, interleukin 8 gene expression was comparable in IVDs injected with chondrocytes and in intact disks as control (P = 0.647), whereas its expression in IVDs injected with saline increased 50-fold (P = 0.028). Transgene expression of red fluorescent protein, &bgr;-galactosidase, and human bone morphogenetic protein 7 diminished at 8 wks after injection. IVDs injected with chondrocytes overexpressing human bone morphogenetic protein 7 did not show lower interleukin 8 gene expression or improved histology. Macrophages were consistently detected by immunohistochemistry in the cartilage formed around the needle insertion sites in both the saline and chondrocyte groups, whereas neither T cells nor neutrophils were detected. ConclusionsAllogeneic rabbit articular chondrocyte survived in the degenerating rabbit IVDs for at least 8 wks. Cell treatment resulted in reduced IVD inflammation but did not significantly improve IVD structure.

PDGF-BB Delays Degeneration of the Intervertebral Discs in a Rabbit Preclinical Model.

Study Design. Preclinical animal study. Objective. Determine the in vivo effects of platelet-derived growth factor BB (PDGF-BB) delivered in a thiol-modified hyaluronic acid (TMHA) hydrogel on intervertebral disk (IVD) degeneration. Summary of Background Data. IVD degeneration is a worldwide health concern and remains without an effective treatment. Several in vitro studies have demonstrated the potential of PDGF-BB, a primary component of platelet-rich plasma, as a therapy for IVD degeneration. Our hypotheses were that treatment of injured IVDs with PDGF would inhibit degeneration and that administration of PDGF in a TMHA hydrogel would improve its efficacy. Methods. IVD degeneration was induced using the rabbit annular puncture model. Four weeks after injury, IVDs were treated with either PDGF-BB or PDGF-BB delivered within a TMHA hydrogel. The efficacy of treatment was determined using x-ray, MRI, histology, and biomechanical testing. Results. At 4 weeks after treatment, cell apoptosis and deposition of matrix containing type III collagen a1 (Col3a1) was demonstrated in both the nucleus pulposus and annulus fibrosus, while this was inhibited by PDGF. At 8 weeks after treatment, disc area and MRI indices of injured IVDs treated with PDGF were significantly higher (P < 0.05) than those treated with the TMHA alone. Similarly, degenerative scores for saline- and TMHA-treated IVDs demonstrated significantly more degeneration (P < 0.05) than PDGF-treated IVDs at 8 weeks. Biomechanical assessments found fewer indicators of degeneration in PDGF-TMHA-treated IVDs at both 4 and 8 weeks post-treatment, compared to saline-, TMHA-, and PDGF-only-treated IVDs. Both PDGF- and PDGF-TMHA-treated IVDs also demonstrated a significant increase (P < 0.05) in compressive strength to failure, compared with controls at 8 weeks post-treatment. Conclusion. The results of this study suggest that PDGF-BB significantly decreases disc degeneration and when delivered in a TMHA gel scaffold, helps prevent both apoptosis and Col3 matrix production, while maintaining disc structure and biomechanical function. Level of Evidence: NA

PDGF-BB inhibits intervertebral disc cell apoptosis in vitro.

Degeneration of the intervertebral disc (IVD) results in deterioration of the spinal motion segment and can lead to debilitating back pain. Given the established mitotic and anti‐apoptotic effects of recombinant human platelet‐derived growth factor‐BB (rhPDGF‐BB) in a variety of cell types we postulated that rhPDGF‐BB might delay disc cell degeneration through inhibition of apoptosis. To address this hypothesis, we treated human IVD cells isolated from five independent patients with rhPDGF‐BB in monolayer and 3D pellet cultures. The anti‐apoptotic potential, cell proliferative capacity, morphology/pellet differentiation, and gene expression of PDGF‐treated IVD cells were evaluated via flow cytometry/immunohistochemistry, MTT assays, histology, and quantitative RT‐PCR, respectively. We found that rhPDGF‐BB treatment significantly inhibited cell apoptosis, increased cell proliferation and matrix production, and maintained mRNA expression of critical extracellular matrix genes. This study suggests two possible mechanisms for the anti‐degenerative effects of rhPDGF‐BB on human IVD cells. First, PDGF treatment strongly inhibited IVD cell apoptosis in 3D cultures. Second, rhPDGF‐BB acts as an anabolic agent, promoting maintenance of IVD cell phenotype in 3D culture, based on the molecular and protein expression analysis. We speculate that rhPDGF‐BB may be used as a biologic treatment to target early degenerative IVD disease in the future.

Retroperitoneal approach to the intervertebral disc for the annular puncture model of intervertebral disc degeneration in the rabbit

BACKGROUND CONTEXT The rabbit annular puncture model of degeneration is among the most widely used models of intervertebral disc (IVD) degeneration. There are no published reports of the specific surgical technique used to produce this model. PURPOSE To describe the model in detail in an effort to reduce center-to-center variability and hopefully improve the reproducibility of future experimental results. STUDY DESIGN Technical report of surgical approach and experience. PATIENT SAMPLE New Zealand White Rabbits. METHODS A detailed report of the annular puncture technique in rabbits is provided including preparation of the animals, instrumentation, a description of retroperitoneal approach to the lumbar area, and the technique for IVD injury. Common pitfalls and complications of the procedure are described. CONCLUSIONS The methods described can serve to standardize the implementation of this important preclinical model of disc degeneration.

The Nonsurgical Treatment of Back Pain

Each spinal motion segment is a three-joint complex comprised of the intervertebral disc, two facet joints, and a host of ligamentous and muscular attachments. This complex allows for multiaxial movement and loading of the spine while maintaining an upright posture and protection of the neural elements. The anatomic complexity of this articulation has complicated the search for a specific pathoanatomic cause for low back pain. The most common etiologies can be broadly categorized as neural, muscular, osseous, disc-related, and facet-related and have been the subject of much debate (Lutz et al. 2003). In the early decades of the twentieth century, nerve dysfunction, including neuritis and neuralgia, as well as muscular dysfunction were proposed as the leading causes of back pain. As the use of radiographs became more widespread, the classic bony changes associated with disc degeneration and spondylosis were found in many patients complaining of low back pain; hence, osseous etiologies became a popular theory. Initially, an inflammatory etiology for these bony changes was assumed; however, when no consistent marker of inflammation was found, it was then seen as a degenerative disorder. In the late 1930s and early 1940s, intervertebral disc pathology began to be recognized as a major low back pain generator (Barr 1938; Key 1945) and became the dominant theory for several decades. This resulted in an increase in the number and variety of surgical procedures directed at the intervertebral disc. By the end of the twentieth century, evidence emerged that anatomic abnormalities, as visualized by diagnostic imaging tests, often did not correlate with clinical symptoms (Boden et al. 1990). As a result, most modern treatments for low back pain are pragmatic in approach rather than searching for a specific anatomic directed cause (Lutz et al. 2003), with nonsurgical intervention taking center stage.

Effects of Wnt5a Haploinsufficiency on Bone Repair.

Objectives: Wnt5a expression is upregulated during fracture repair and has previously been implicated as a potential regulator of skeletal development and bone mass accrual and maintenance. Our objective was to evaluate the function of Wnt5a in fracture healing. Methods: Femoral fracture experiments on Wnt5a+/+ and Wnt5a+/− mice were carried out. To better understand the effect of the Wnt5a on bone repair, we evaluated radiographs using a previously validated qualitative scoring system and performed microcomputed tomography analyses. Histomorphometric analyses determined the temporal distribution of stroma, cartilage matrix, and woven bone in the fracture callus. Finally, we performed tartrate-resistant acid phosphatase (TRAP) immunohistochemical staining to visualize and quantify bone resorbing cells. Results: Radiographic evaluations at day 21 demonstrated significantly higher cortical remodeling and bridging parameters for the Wnt5a+/− group compared with the Wnt5a+/+ group. The bone volume fraction by microcomputed tomography was also significantly increased in Wnt5a+/− mice. Histological and histomorphometric analyses showed that although Wnt5a+/− mice exhibit decreased cartilage matrix production at day 7 postfracture, they displayed increased residual cartilaginous callus at days 14 and 21 compared with the Wnt5a+/+ group. In addition, the total number of multinucleated tartrate-resistant acid phosphatase–positive cells was significantly lower in the Wnt5a+/− group than in the Wnt5a+/+ group. Conclusions: The data indicate that decreased Wnt5a signaling impaired proper fracture healing, possibly through decreased cartilaginous callus formation, and delayed cartilage matrix and mineralized tissue remodeling within the fracture callus.

Manual unloading of the lumbar spine: can it identify immediate responders to mechanical traction in a low back pain population? A study of reliability and criterion referenced predictive validity

Background:: To date, no research has examined the reliability or predictive validity of manual unloading tests of the lumbar spine to identify potential responders to lumbar mechanical traction. Purpose:: To determine: (1) the intra and inter-rater reliability of a manual unloading test of the lumbar spine and (2) the criterion referenced predictive validity for the manual unloading test. Methods:: Ten volunteers with low back pain (LBP) underwent a manual unloading test to establish reliability. In a separate procedure, 30 consecutive patients with LBP (age 50·86±11·51) were assessed for pain in their most provocative standing position (visual analog scale (VAS) 49·53±25·52 mm). Patients were assessed with a manual unloading test in their most provocative position followed by a single application of intermittent mechanical traction. Post traction, pain in the provocative position was reassessed and utilized as the outcome criterion. Results:: The test of unloading demonstrated substantial intra and inter-rater reliability K = 1·00, P = 0·002, K = 0·737, P = 0·001, respectively. There were statistically significant within group differences for pain response following traction for patients with a positive manual unloading test (P<0·001), while patients with a negative manual unloading test did not demonstrate a statistically significant change (P>0·05). There were significant between group differences for proportion of responders to traction based on manual unloading response (P = 0·031), and manual unloading response demonstrated a moderate to strong relationship with traction response Phi = 0·443, P = 0·015. Discussion and conclusion:: The manual unloading test appears to be a reliable test and has a moderate to strong correlation with pain relief that exceeds minimal clinically important difference (MCID) following traction supporting the validity of this test.